1842-10-20: Commodore Jones mistakenly tries to take California for the U.S.

Under the impression that the U.S and Mexico were at war, Commodore Jones mistakenly tries to take possession of California in Monterey for the US. Thomas O. Larkin told him that there is no war between the U.S. and Mexico. Monterey was restored to Mexico the next day.

Fink, Augusta. Monterey: The Presence of the Past. San Francisco: Chronicle Books, 1972. p. 78.

“On October 20, 1842, the fort [Monterey Presidio] was taken by U.S. Navy Commodore Thomas ap Catesby Jones, commander of the Pacific Squadron, who mistakenly believed the United States and Mexico were then at war. El Castillo was renamed Fort Catesby (popularly called Jones’ Fort in many journals of the day) and remained such for one day, until Jones learned of his error, apologized, and reinstated the Mexican standard.”

http://www.militarymuseum.org/Monterey.html

http://en.wikipedia.org/wiki/Thomas_ap_Catesby_Jones